3 analogWrite Pins on Nano causing Serial.read to hang

Hardware
1

Hello! We are attempting to use a Nano to drive an RGB LED strip, using analogWrite on pins 9, 10, 11, which drive a MOSFET allowing 12V power to the LEDs. The Nano receives an RGB string through serial, such as "255,0,0", which would indicate that the red pin should be fully on, and green and blue should be turned off.

The code below works fine as long as I use 255 and 0 only (all the way on or all the way off). However, if I have any other input (e.g. (120,120,0)), the Serial stops accepting new input.

Based on my research, it seems to have something to do with PWM and the interrupts required for Serial to work, but I'm a little at a loss as to how to proceed, given that driving the LEDs using PWM is a requirement.

Code is included below. Thanks for your help!

int redPin = 9, greenPin = 10, bluePin = 11;

int allPins[3] = {redPin, greenPin, bluePin};

void setup() {
  for (byte i = 0; i < 3; i++) {
    pinMode(allPins[i], OUTPUT);
  }

  Serial.begin(115200);
  Serial.setTimeout(20);

  for (byte i = 0; i < 3; i++) {
    analogWrite(allPins[i], 0);
  }
  
}

void loop() {
  checkRgb();
}

void checkRgb() {
  if (Serial.available() == 0) return;   //wait for data available
  String teststr = Serial.readString();  //read until timeout
  teststr.trim();                        // remove any \r \n whitespace at the end of the String
  handleRgbString(teststr);
}

bool handleRgbString(String teststr) {
  int strLen = teststr.length() + 1;
  char char_array[strLen];
  teststr.toCharArray(char_array, strLen);
  char delimiters[] = ",";
  char* valPosition;

  String redString = strtok(char_array, delimiters);

  if (!isValidNumber(redString)) return false;

  String greenString = strtok(NULL, delimiters);

  if (!isValidNumber(greenString)) return false;

  String blueString = strtok(NULL, delimiters);

  if (!isValidNumber(blueString)) return false;

  analogWrite(redPin, redString.toInt());
  analogWrite(greenPin, greenString.toInt());
  analogWrite(bluePin, blueString.toInt());

  return true;
}

boolean isValidNumber(String str) { //TEST THIS LOGIC
  for (byte i = 0; i < str.length(); i++)
  {
    if (!isDigit(str.charAt(i))) return false;
  }
  return true;
}
2

Is this a 'classic' Nano? Unfortunately there are different Arduinos namend 'Nano'.
On a classic Nano pin 11 is not PWM capable. You can use pin 12 instead.
I don't know what happens if you use pin 11 with analogWrite().

3

It looks like you confused Arduino pins and mcu pins. On nano Arduino pins 9, 10 & 11 are PWM outputs

4

Thanks for the reply - this is a classic arduino nano (atmega328)

5

No, but obviously in the pinout illustration I used, pins 11 and 12 are reversed. In another picture it was ok. I guess I will have to dispose of that picture, sorry :wink:

6

Thanks for the clarification - let me know if you have any other thoughts.

7

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.